Time‑Speed‑Distance (T‑S‑D) – Quick & Easy Study Notes
(Lakshadweep Forest Guard, Quantitative Aptitude)
1. What Is It?
Think of a road trip:
- Distance = How far you travel (km, miles).
- Speed = How fast you go (km/h, mph).
- Time = How long the trip takes (hours).
The relationship is: Distance = Speed × Time.
So if you know any two of these, you can find the third.
2. Simple Formulas
| Want to find | Formula (plain words) |
|---|---|
| Time | Time = Distance ÷ Speed |
| Speed | Speed = Distance ÷ Time |
| Distance | Distance = Speed × Time |
Remember:
- ÷ = divide, × = multiply.
- Be consistent with units (all km, all hours, etc.).
3. Everyday Analogies
| Situation | What You Know | What You Need | How To Use the Formula |
|---|---|---|---|
| Going from home to the market | Distance = 10 km | Speed = 50 km/h | Time = 10 ÷ 50 = 0.2 h (12 min) |
| Speed of a train | Speed = 80 km/h, Time = 2 h | Distance | Distance = 80 × 2 = 160 km |
| Planning a walk | Time = 1 h, Distance = 4 km | Speed | Speed = 4 ÷ 1 = 4 km/h |
4. Tiny Example
Problem
A forest guard walks 5 km to a lookout point at a steady pace of 3 km/h. How long does it take?
Solution
Time = Distance ÷ Speed = 5 ÷ 3 ≈ 1.67 h
≈ 1 hour 40 minutes.
5. Quick Tips
- Check Units First – If distance is in km and speed in km/h, time will be in hours.
- Convert Minutes if Needed – 1 hour = 60 minutes.
- Look for “Average Speed” – If a trip has two parts with different speeds, find the average speed by dividing total distance by total time.
- Use “÷” for Division – In mental math, think “divide the distance by the speed.”
6. Mini Practice Problems (Try on Your Own)
| # | Problem | Answer |
|---|---|---|
| 1 | A bike covers 30 km in 2 hours. What is its speed? | 15 km/h |
| 2 | A jeep travels 120 km at 60 km/h. How long did it take? | 2 h |
| 3 | You walk 8 km at 4 km/h. How many minutes did it take? | 120 min (2 h) |
| 4 | A forest patrol car drives 45 km in 0.75 h. Find the speed. | 60 km/h |
| 5 | A train covers 200 km in 4 h. If it stops for 30 min, what is the average speed? | 45 km/h (total time 4.5 h) |
Hints
- For #3, multiply hours by 60 to get minutes.
- For #5, add the stop time to the travel time before dividing.
7. Recap
- Distance = Speed × Time
- Use the two known values to find the third.
- Keep units the same.
- Convert hours to minutes when needed.
With these simple steps, you can solve any T‑S‑D question quickly and confidently!